The cellular oncogenes are a cohort of normal cellular gens which are avidly conserved across a broad span of evolution. Preliminary evidence indicates that their conservation may be due to central roles in normal cellular proliferation and/or differentiation. We have previously demonstrated expression of some cellular oncogenes (c-oncs) during murine embryogenesis. We have expanded on the work and in this proposal we present preliminary data concerning the expression of other c-oncs during murine development. Using techniques to localize those cells and tissues responsible for expression of a given c-onc, we wish to further analyze the role that these genes may play in the physiologic processes of normal development. Inappropriate expression of c-oncs has been implicated as a contributory event in the induction and/or maintenance of malignancy. Other investigators have obtained evidence for transcription of some c-onc genes in a limited number of fresh human tumors. In this proposal we present preliminary results of studies designed to examine the expression of 15 different c-oncs in 14 fresh human tumors and corresponding normal tissue. We propose to carry out an extensive survey of a wide variety of human tumors for c-onc gene expression. Tissues will be analyzed for differential c-onc gene expression (malignant vs. normal), localization of cells responsible for expression within a given tissue, and tumor-related patterns of expression.